Knife sharpener



Nov. 8, 1960 JEPSON KNIFE SHARPENER Filed Aug. 18, 1958 III/'II/ KNIFESHARPENER Ivar Jepson, Oak Park, Ill., assignor to Sunbeam Corporation,Chicago, 111., a corporation of Illinois Filed Aug. 18, 1958, Ser. No.755,624

3 Claims. (Cl. 51-116) The present invention relates to a knifesharpener, and more particularly to a household type of knife sharpener.

Small power driven knife sharpeners for use in the home to sharpenkitchen knives and the like are well known in the appliance field. Suchsharpeners commonly employ several rotating wheels or discs betweenwhich the knife to be sharpened is drawn. The two abrasive discs arefrequently mounted coaxially and are driven by a small electric motor.Although the use of two grinding wheels permits both sides of the knifeto be sharpened at the same time, such an arrangement presents problemswith respect to obtaining the proper angle benited States Patent tweenthe grinding wheels and the blade being sharpened.

'In sharpening a knife, it is desirable to shape the cutting edge sothat it has a narrow angle defined by the intersecting surfaces of theblade.

Regardless of how the surfaces of two axially spaced grinding discs areshaped, I

this desired angle at the cutting edge, it is necessary to have thegrinding surfaces overlapping so they define a it is difficult to obtaina well defined angle on the cutting edge which terminates at a sharp,even apex. To obtain sharp angle. It would be desirable, therefore, toprovide a knife sharpener having overlapping grinding surfaces to permitthe grinding of a well defined angle at the cutting edge.

It has also been found that a grinding wheel in a knife sharpener shouldrotate in a particular direction with fore, preferable to have thegrinding wheels or discs moving a direction from the cutting edge towardthe back of the knife in the area of engagement. In the convention'alsharpeners having the co-axially aligned discs,

both types of relative engagement are obtained between the blade and theabrasive discs resulting in a feather vedge along at least a portion ofthe blade. It would be desirable, therefore, to have a knife sharpenerin which guiding means are provided to insure engagement between theknife blade and the grinding wheels in an area in which the grindingwheels would be moving from the cutting edge toward the back of theknife. I It is accordingly an object of the invention to provide a newand improved knife sharpener.

Another object of the invention is to provide a knife sharpener havingoverlapping grinding surfaces and knife guiding means insuring properengagement of the knife by the grinding surfaces and without any dullingeffect on the knife.

Still another object of the invention is to provide a knife sharpener inwhich the drivingmotor and grinding wheels 3 are mounted on a frame toform a unit insertable into a hollow housing provided with a knifeguiding slot and also having index means to precisely locate the unitrelative to the slot.

A further object of the invention is to provide a knife 37 .plateportions 17 and 18 which extend upwardly on sharpener in which a switchactuator forms a segment of the housing and carries switch contactsthereon together with stop means in the housing for pressing thecontacts together as the actuator is pressed inwardly of the housing.

Further objects and advantages of the present invention will becomeapparent as the following description proceeds, and the features ofnovelty which characterize the invention will be pointed out withparticularity in the claims annexed to and forming a part of thisspecification.

For a better understanding of the present invention, reference may behad to the accompanying drawings in which:

Fig. 1 is a perspective view of a knife sharpener forming one embodimentof the invention and during use to sharpen a knife;

Fig; 2 is an enlarged, fragmentary, vertical section of the knifesharpener shown in Fig. 1 and taken along line 2-2 of Fig. 3 showing themotor in full lines and portions of the switch;

Fig. 3 is an enlarged top plan view of the internal mechanism of theknife sharpener with a portion of the housing cut away;

Fig. 4 is an enlarged, fragmentary, vertical section of the knifesharpener taken along line 44 of Fig. 2 with only one of the grindingwheels shown in full; and

Fig. 5 is an enlarged, fragmentary section of a portion of the knifesharpener and showing an actuating switch thereof.

The present invention provides a knife sharpener including a pair ofoverlapping cup-shaped grinding wheels :driven at different rotationalspeeds such that the speed of the rims of the wheels are the same. Theknife sharpener mechanism including the grinding wheels fits into acup-shaped housing of plastic having a slot in the upper end thereof.Portions of the mechanism frame engage projections on the housing andnotches in the housing to precisely locate the grinding wheels in aposition in which only the proper side of the wheels can be engaged by aknife in the slot. The housing has an opening toward which a plasticplate carrying switch contacts is urged. When the plate is pressedmanually inwardly from the opening, one of the contacts engages a stopin the housing and closes on the other contact.

There is shown in the drawings a knife sharpener which includes a pairof grinding wheels 10 and 11 forming a part of a unitary assemblyincluding frame members 12 and 13 and an electric motor 14. The framemembers 12 and 13 consist of two vertically disposed, spaced platemembers between which the electric motor 14 is clamped. The unitaryassembly fits into a plastic casing or housing 15 composed of plasticmaterial such as vinyl or other suitable plastic material. The housing15 is provided with a slot 16 for aligning a knife K (Fig. l) with thewheels 10 and 11 and limiting engagement of the knife to portions of thegrinding wheel which are rotating in a direction for the best sharpeningaction. The guide slot keeps the knife blade out of contact with theother'portions of the grinding wheels. To prevent movement of theunitary assembly relative to the slot 16, the frame members 12 and 13are provided with upstanding arcuate the outside of the grinding wheels10 and 11.

A pair of ribs or bracket projections 19 and 2 0 are formed integrallywith the housing 15 and extended across the bottom of the upper wall ina direction parallel to the guide slot 16. The arcuate plate portions 17and 18 are shaped to fit the concave upper wall ofhousing 15 and arespaced to straddle the bracket projections 19 and 20. The engagementbetween the plate portions 1'! and I8 and the bracket projections 19 and20 assures accurate location of the unitary assembly carrying ath'egrinding wheels and 11 with respect to the slot 16. Any misalignmentbetween slot 16 and the grinding wheels 10 and 11 would, of course,result in the knife K engaging the grinding wheels 01f center and havingthe cutting edge ground off center.

To form a grinding chamber within which the grinding wheels 10 and 11are mounted, the frame members 12 and 13 are formed with inwardlyprojecting arcuate walls or shelves 25 and 26 respectively. The arcuatewalls 25 and 26 ext-end above the motor 14 and abut each other along aplane defined by the slot 16. As can be best seen in Fig. 4, the wall 26extends outwardly to engage the walls of casing 15. Similarly, the wall26 also engages adjacent portions of casing 15. The walls 25 and 26together with the plate portions 17 and 18 cooperate with the casing toform an enclosure or chamber for the. grinding wheels 10 and 11. Withthe grinding wheels separated from the motor 14, the abrasive grit andfilings associated with the sharpening operation are kept, out of themotor where they might cause malfunctioning.

In order to further limit relative movement between casing 15 and theunitary assembly with its associated grinding wheels 10 and 11, thereare provided notches 21 and 22 (Fig. 4) located at the ends of the slot16 and extending transversely thereto. The notches 21 and 22 are formedby overhanging bars or ribs 23 and 24 molded integrally with the housing15. End portions of arcuate shelves 25 and 26 fit into the notches 21and 22, respectively.

To assemble the frame members 12 and 13 with the motor 14 therebetween,a pair of cap screws 27 are employed which extend through clearanceholes in frame member 12 and the field assembly of motor 14 and engagetapped holes in the frame member 13. The motor 14 is thus located andclamped between the frame members to form the unitary assembly. Toinsure proper alignment of the frame members 12 and 13, the portionsofthe frame members which engage the motor 14 are in the form ofinwardly extending bosses 29 which surround the cap screws 27 and havetheir faces machined for accurate engagement with the field of motor 14.

The cup-shaped housing 15 is retained in assembled relation to the framemembers 12 and 13 by four cap screws 30. To support the cap screws 30,the frame members 12 and 13 have four casing assembly lugs 32 whichextend outwardly in a horizontal plane from each corner of the unitaryassembly including frame members 12 and 13. Each lug 32 has a clearancehole formed therein to accommodate one of the upwardly extending capscrews 30. To receive the ends of the cap screws 30, the cup-shapedhousing 15 is formed with downwardly projecting posts 31. The cap screws30 extend upwardly through the holes in the lugs 32 into threadedengagement with the posts 31 to draw the lugs against the ends of posts31.

The motor 14 is provided with an armature shaft 41 on which are securedand keyed thereto gears 42 and. 43 and a cooling fan 44. To enclose themotor completely, the housing 15 is provided with a bottom cover plate46 which serves as a closure for the bottom opening in housing 15. Toprevent the motor 14 from overheating within the casing, a pair of airvent openings 45 and 47 are provided in the cover plate 46. The fan 44rotates in such'a direction to draw air in through inlet opening 45 onone side of the cover plate 46 and discharge it through the outletopening 47 on the opposite side of the cover plate. The cover plate issecured to the frame members 12 and 13 by cap screws 48 and fits into aninner groove 49 in the housing 15. The gears 4'2 and 43 mesh with anddrive gears 52 and 53 keyed to shafts 54 and 55, respectively. Theshafts 54 and 55 are journaled in bushings 56 in bores 57 formed in themembers 12 and 13 at precise angles relative to one another such thatthe shafts 54 and 55 tilt both upwardly and toward the back of thehousing 15 as illustrated in Figs. 2 and 3.

Because of the angle between the armature shaft 41 and the shafts 54 and55 mounting the grinding discs, bevel gears are used for gears 42, 43,52 and 53.

In one constructed embodiment of the invention, the angle between theaxis of each of the shafts and the horizontal was about twenty degrees.The angle between the axis of each of the shafts and a vertical planethrough the armature shaft was about three and one-half degrees. Both ofthe grinding wheels 10 and 11 are cup-shaped having central baseportions 10a and 11a respectively. To permit mounting of the grindingwheels 10 and 11 on the shafts 54 and 55, the central portions 10a and11a are provided with holes or apertures 10b and 11b which receive themounting means. To accomplish the mounting of grinding wheel 10 on shaft54, a pair of metal washer-like members 58 and 59'are keyed to a nut 60with the grinding wheel clamped between the washers. To maintain thegrinding wheel centered with respect to shaft 54, the washer 58 isformed with a shouldered portion 58a which is received in the hole 10bin the grinding wheel. The nut 60 is threadedly received on the end ofshaft 54 to complete the assembly of grinding wheel 10 to the shaft.Similarly the grinding wheel 11 is secured to shaft 55 by washer-likemembers 61 and 62 keyed to a nut 63 threaded on the upper end of theshaft 55.

The grinding wheels 10 and 11 are formed with cylindrical side walls 10cand 110 respectively which extend from the central portions 10a and 11aof the grinding wheels. The, outer edges of the side walls and terminatein grinding faces 10d and 11d respectively which consist, of annularsurfaces substantially perpendicular to the axes of shafts 54 and 55respectively. Because of the orientation of the shafts 54 and 55, it isnecessary to have the faces 10d and 11d slightly conical in shape. Inthe constructed embodiment in which the shafts angled three and one-halfdegrees from the vertical plane through the axis of the armature shaftthe surfaces 10d and 110? were angled such that any radial segmentthereof defined an angle of 3 /2 degrees with a plane perpendicular tothe axis of shaft 54 or shaft 55 respectively. The grinding wheel 10 hasan external diameter of portion 100 which is slightly less than theinner diameter of the cylindrical portion 110 of the cupshaped wheel 11.The wheel 10 is positioned so that its lower portion projects into thewheel 11 and the planes defined by the grinding faces 10d and 11doverlap. By reason of the overlapping relationship of the grinding faces10d and 11d, each face engages the cutting edge of the knife K when theknife is resting on an end portion or knife rest 64 of the groove 16.

The shafts 5'4 and 55 and the wheels 10' and 11 are tilted slightly inthe horizontal plane to form an angle preferably of about three andone-half degrees in a horizontal direction toward the back of thehousing 15 away from the knife rest 64. When the knife is resting on theknife rest 64 and against the wheels 10 and 11, it is engaged only bythe portions of grinding faces 10d and 11d which are positioned towardthe front of the housing. These portions are designated by numerals 65and. 66 in Fig. 3. The motor 14 drives the wheels 10 and 11 in the samedirection which is such that the portions of the rims of the wheelnearest the stop 64 or the front of the housing are being moved upwardlyso that grinding occurs from the cutting edge toward the back of theknife K which provides the best sharpening action. Because of theslightly conical shape provided on the grinding faces 10d and 11d, theknife edge when resting on the knife rest or stop 64 is engaged acrossthe entire widths of the faces 10d and 11d at the points of engagement65 and 66.

Means have been provided so that the grinding faces 10d and 11d of thewheels 10 and 11 travel at substantially the same linear speed. Sincegrinding faces 10d and 11d have different diameters, the equality inlinear speed is accomplished by having different gear ratiosv betweenthe gears 42 and 52 and respectively. The gear, 43 is smaller than thegear 42 Y and the gear 53 is larger than the gear 52 by such amounts tae the gears 43 and 53,

that the face d ofthe wheel v10 has the same linear The bar 23 of thehousing is positioned sufiiciently low,

and in engagement with the wheels 10 and 11, but the 8 bar 23 ispositioned sufiiciently high that when the knife edge is moved away fromthe knife rest 64 and moved into only the portions 65 and 66 of thewheels 10 and 11 on the other side of the wheels from the bar 23. Hence,the knife edge is kept out of contact with the portions of the wheels 10and 11 moving downwardly relative to the knife blade. Consequently,grinding across the blade toward the cutting edge never occurs with thesubject invention.

Electric power is supplied to the motor 14 from electric cord 71 passingthrough a suitable opening at the rear of the housing 15. One conductor(not shown) of the cord 71 is connected directly to the motor as is wellknown in the art and the other conductor 72 is connected to a switch 69which is made up of a pair of vertically extending L-shaped contactsprings 73 and 77. The switch 69 is mounted on and operated by apivotally mounted plate member 75 which is fabricated of some suitableinsulating material such as plastic. To pivotally mount the plate member75 on the frame members 12 and 13, a pair of spaced, parallel arms 79extend upwardly and are pivotally connected by pins 80 to lugs 81 whichproject from the frame members 12 and 13.

The bottom of the plate member 75 is provided with an inwardlyprojecting, elongated boss 74 which serves to mount the L-shaped contactsprings 73 and 77 Screws 76 and 78 are threadedly received in boss 74 tosecure the contact springs 73 and 77 respectively to the plate member75. Contact springs 73 and 77 each have horizontally extending legs 84and 85 which extend in overlapping relation as can be best seen in Fig.2. The contact springs 73 and 77 are inclined upwardly at slightlydifferent angles so that the legs 84 and 85 are spaced from each otherwhen the contact springs are in the open position for the switch 69.

The switch is connected in the circuit by the conductor 72, of powercord 71, which is secured to the spring contact 73 by means of screw 76.The other contact spring 77 is connected to the motor by a conductor(not shown).

To deflect spring contact 77 into engagement with spring contact 73 whenthe plate member 75 is rotated, a ceramic button 82 is mounted on theinside face of the spring contact 77 in engagement with the field of themotor 14. To limit the clockwise rotation of the plate member 75 aroundthe pivot pins 80, there are a pair of cars 83 formed integrally withplate member 75 and extending outwardly therefrom to engage the casing15. The plate member 75 is normally biased in a clockwise direction bythe spring contact 77 which is in a deflected position when button 82 isin contact with the motor 14 and ears 83 are engaged with the casing 15.Thus the spring contact 77 tends to bias the switch to the open positionin which plate member 75 is rotated in the clockwise direction to thefull extent of its travel.

When the plate member 75 is pressed inwardly rotating itcounterclockwise around its pivotal mounting, the spring contact 77deflected to a greater extent until the leg 85 of the spring contact 77is brought into contact with leg 84 of the spring contact 73. Thisengagement between legs 84 and 85 completes the circuit through motor 14and energizes the motor.

To the motor 14, the user of the sharpener presses viewed in Fig. 4,that clearance for the knife K is provided when the knife K rests on theknife rest 64 engagement with the bar 23, the knife edge will engage r 6against theplate 75 which pushes the contact 77 into engagement with thecontact 73. The laterally projecting legs or end portions 84 and 85 ofthe contacts 73 and 77 overlap and engage one another to form thecontact portions ,of the switch. Then, when it is desired totie-energize the motor 14, the user releases the plate 75. The contact77, being of leaf spring construction, urges the plate 75 back in theclockwise direction, as viewed in Fig. 5, and the ends of springcontacts 73 and 77 separate. Molded feet 89 of known construction aresecured by screws to the bottom cover plate 46 and sup port thesharpener in a position elevated above the table top or other surface onwhich it is used so that cooling air is free to enter the inlet '45 andflow from the outlet 47. I a

The positions of the wheels 10 and 11 tilted toward the back of thehousing 15 and upwardly, together with the flat, slightly frustoconicalrims of the wheels, insome that the faces 10d and 11d of the wheelscontact the edge of the knife being ground. The position of the kniferest 64 relative to the wheels 10 and 11 causes the knife edge to alwaysbe contacted by the portions of the grinding wheels 10 and 11 which aremoving upwardly against the cutting edge of the knife. By the provisionof the projections 19 and 20 and the arcuate plates 17 and 18, theassembly is precisely located and held against movement transversely ofthe slot 16, and the notches 21 and 22 and the shelves 25 and 26interlock with one another to precisely locate the grinding wheels 10and 11 longitudinally of the slot 16. This indexing structure is preciseand rugged while being simple and inexpensive in its fabrication andassembly. In addition, the arcuate plates 17 and 18 cooperate with theshelves 25 and 26 and the casing 15 to form a grinding chamber separatedfrom the housing portion. The switch unit including the pivotallymounted actuating plate 75, which also carries the switch contacts 73and 77 also is simple, effective and inexpensive. This switch unit doesnot require a separate cover and contact mounting and actuating means,and has a minimum of moving parts.

While there has been shown and described one particular embodiment ofthe present invention, it Will be apparent to those skilled in the artthat various modifications may be made without departing from theinvention in its broader aspects, and it is therefore aimed in theappended claims to cover all such changes and modifications as fallwithin the true spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. In a knife sharpener, a pair of cup-shaped grinding wheels, the rimof one of said wheels being adapted to fit partially into the rim of theother of said wheels, a housing having a knife guiding slot extendingacross the top thereof from front to rear, means mounting said wheelsrotatably in said housing generally on opposite sides of said slot inpositions in which the lower portion of the rim of said one of saidwheels extends into the lower portion of the rim of said other of saidwheels, said mounting means mounting said wheels on axes of rotationsuch that the openings in said cup-shaped wheels open toward the top andback of said housing, the opposed faces of said grinding wheels beingconical in shape, one end of said slot defining a knife rest upon whicha knife blade may be supported during sharpening, said rest beingpositioned along a line defined by the intersection of the conesincluding said conical faces of said grinding wheels, and a stop at theother end of said slot positioned above a line defined by theintersection of two planes each normal to the axis of each grindingwheel and passing through the outermost edge of each grinding wheel.

2. A knife sharpener comprising an electric motor, a frame mounting saidelectric motor having a pair of spaced end plates extending upwardlytherefrom, an in verted cup-shaped housing enclosing said motor, a knifereceiving slot in said housing, said end plates abutting said housing oneither side of said slot, wall means on said frame cooperating with saidend plates and said housing to form .a chamber between said end platesclosed except for said slot, a pair of grinding wheels mounted forrotation in said chamber adjacent said slot, drive meansconnecting'saidmotor and said grinding wheels.

3. A knife sharpener comprising an electric motor, a frame mounting saidelectric motor having a pair of spaced end plates extending outwardlytherefrom, a housing member for said motor engaging said end plates, 21pair of grinding wheels mounted for rotation between said end plates,drive means connecting said motor and said 15 2,365,1 1

8 grinding wheels, wall means on said frame cooperating with said platesand said housing to form a compartment for said grinding wheelsseparated from said motor, and a knife receiving slot in said housingproviding access to said compartment and said grinding wheels.

References Cited in the file of this patent UNITED STATES PATENTS1,606,813 Schultz Nov. 16, 1926 1,946,311 7 'Comeau Feb. 6, 19342,019,471 Broberg Oct. 29, 1935 2,722,783 ORussa Nov. 8, 1955 2,775,075McMaster et a1 Dec. 25, 1956 Madl et a1. Dec. 23, 1958

